Definition
A high-update-rate radar surveillance system used by air traffic control to monitor independent simultaneous approaches to closely spaced parallel runways. The PRM system uses a fast-scanning radar (typically updating once per second or faster) combined with high-resolution displays and automated alerting to detect any aircraft deviating from its assigned approach course toward the adjacent runway, allowing controllers to issue immediate breakout instructions before a collision risk develops.
Plain English
A special radar setup that lets controllers run two parallel landings at the same time on runways that are close together. It updates very quickly and warns the controller right away if an aircraft drifts toward the other runway, so they can tell that aircraft to turn off the approach immediately.
Context Anchor
You may encounter this term on instrument approach charts, in ATIS information, in approach clearances, or during briefings at airports that use closely spaced parallel runways.
Derivation
Precision refers to the high accuracy and fast update rate of the radar. Monitor signals its purpose: it watches the approaches rather than directing them. The radar does not control the aircraft; it watches for any aircraft straying from its assigned path.
Why Pilots Care
Enables safer and more efficient use of airport capacity by allowing simultaneous landings without increasing collision risk.
Grounding Statement
Picture two aircraft lining up for two parallel runways close together; the PRM System helps ATC notice quickly if one aircraft starts moving toward the other aircraft’s lane.
Intuition Check
PRM does not mean the pilot’s own monitoring is simply more precise. It refers to a specific ATC monitoring system and procedure used to manage closely spaced parallel approaches.
Example Sentence 1
Tower advised that PRM monitoring was active for the parallel approaches, so the crew briefed the breakout procedure before beginning the descent.
Example Sentence 2
Due to a deviation detected by the PRM System, we received a breakout instruction and turned away from the parallel traffic.